BRITISH MEDICAL JOURNAL
extract can in no way be considered dangerous. Many wise doctors will safely continue to give thyroid extract to patients who have been well on it for years. Newly diagnosed myxoedema should be treated with thyroxine (or very rarely triiodothyronine), but elderly women on thyroid extract are not living dangerously. P B S FOWLER Charing Cross Hospital, London W6
Beta-blockers in treatment of hypertension SIR,-Dr R G Wilcox's recent comparative study of once-daily hypotensive treatment (5 August, p 383) showed that atenolol 200 mg produced significantly greater effect than the other agents in the doses tested. He rightly points out that the doses of beta-blocking drugs may not have been equipotent, illustrating a potential limitation of fixed-dose comparative studies. Little further hypotensive effect can be expected by increasing the dose of atenolol further,' but this is not necessarily true of the other beta-blocking drugs, and he himself suggests that higher doses of acebutolol or timolol might be more effective. I am able to confirm these speculations in the case of acebutolol from a recent study.' In the twice-daily dose ranging part of this study (n = 11), where the dose of acebutolol was increased above the 400 mg/day used by Dr Wilcox, further falls in blood pressure were produced. This fall in blood pressure was unchanged when each subject's total daily dose was given once daily and blood pressure measured more than 24 h after dosing. Furthermore, there was no increase in the low incidence of side effects. In addition, I found that acebutolol 400 mg produced less beta-blockade, measured as reduction in exercise tachycardia, than atenolol 200 mg (maximum 23+400 v 29+30', P
extract can in no way be considered dangerous. Many wise doctors will safely continue to give thyroid extract to patients who have been well on it for years. Newly diagnosed myxoedema should be treated with thyroxine (or very rarely triiodothyronine), but elderly women on thyroid extract are not living dangerously. P B S FOWLER Charing Cross Hospital, London W6
Beta-blockers in treatment of hypertension SIR,-Dr R G Wilcox's recent comparative study of once-daily hypotensive treatment (5 August, p 383) showed that atenolol 200 mg produced significantly greater effect than the other agents in the doses tested. He rightly points out that the doses of beta-blocking drugs may not have been equipotent, illustrating a potential limitation of fixed-dose comparative studies. Little further hypotensive effect can be expected by increasing the dose of atenolol further,' but this is not necessarily true of the other beta-blocking drugs, and he himself suggests that higher doses of acebutolol or timolol might be more effective. I am able to confirm these speculations in the case of acebutolol from a recent study.' In the twice-daily dose ranging part of this study (n = 11), where the dose of acebutolol was increased above the 400 mg/day used by Dr Wilcox, further falls in blood pressure were produced. This fall in blood pressure was unchanged when each subject's total daily dose was given once daily and blood pressure measured more than 24 h after dosing. Furthermore, there was no increase in the low incidence of side effects. In addition, I found that acebutolol 400 mg produced less beta-blockade, measured as reduction in exercise tachycardia, than atenolol 200 mg (maximum 23+400 v 29+30', P
